Carbon dioxide capture/regeneration method using co-generation

ABSTRACT

New and useful system and method concepts are provided, for removing carbon dioxide from a flow of carbon dioxide laden air. More specifically, a sorbent structure is used in new and useful structures and techniques to bind carbon dioxide in a carbon dioxide laden air stream, and process heat is used to separate carbon dioxide from the sorbent structure and regenerate the sorbent structure.

RELATED APPLICATION/CLAIM OF PRIORITY

The present invention relates to systems and methods for removinggreenhouse gases from an atmosphere, and in particular to systems andmethods for removing carbon dioxide from an atmosphere. In addition, thepresent invention is a continuation of, and further develops conceptsdisclosed in application Ser. No. 12/725,299, filed Mar. 16, 2010, nowU.S. Pat. No. 8,163,066 B2, and entitled Carbon DioxideCapture/Regeneration Structures and Techniques; which is acontinuation-in-part of application Ser. No. 12/124,864, filed May 21,2008, now abandoned, and entitled System and Method for Removing CarbonDioxide from an Atmosphere and Global Thermostat Using the Same; whichis a continuation-in-part of U.S. patent application Ser. No.11/825,468, filed on Jul. 6, 2007, now abandoned, and is acontinuation-in-part of U.S. patent application Ser. No. 11/805,477,filed on May 22, 2007, now abandoned, and is a continuation-in-part ofU.S. patent application Ser. No. 11/805,271, filed on May 21, 2007, nowabandoned, all of which are entitled System and Method For RemovingCarbon Dioxide From An Atmosphere and Global Thermostat Using The Same.All of the foregoing applications are incorporated by reference herein.

BACKGROUND U.S. application Ser. No. 12/124,864

As explained in published U.S. application Ser. No. 12/124,864,

-   -   a. there is much attention currently focused on trying to        achieve three energy related and somewhat conflicting energy        related objectives: 1) provide affordable energy for economic        development; 2) achieve energy security; and 3) avoid the        destructive climate change caused by global warming. Many        different approaches are being considered to address climate        change, including increasing the use of clean, non polluting        renewable energy sources such as biofuels, solar, wind and        nuclear, attempting to capture and sequester the carbon dioxide        emissions from fossil fuel plants, as well as increased        conservation efforts. Some of these approaches, such as solar        power, have had their large scale implementation blocked due to        their current high costs as compared to the cost of fossil based        electricity, and other approaches, such as nuclear, are        restrained by their environmental and security risks. In fact,        the infrastructure and supply for renewable energy is so        underdeveloped (e.g., only about 0.01% of our energy is provided        by solar) that there is no feasible way to avoid using fossil        fuels during the rest of this century if we are to have the        energy needed for economic prosperity and avoid energy        shortfalls that could lead to conflict.    -   b. The climate change threat caused by global warming and the        more general recognition of our need to use renewable resources        that do not harm our planet has grown steadily since the first        Earth Day in 1972. It is mostly undisputed that an increase in        the amount of so-called greenhouse gases like carbon dioxide        (methane and water vapor are the other major greenhouse gases)        will increase the temperature of the planet. These greenhouse        gases help reduce the amount of heat that escapes from our        planet into the atmosphere. The higher the concentrations of        greenhouse gases in the atmosphere the warmer the planet will        be. There are complicated feedbacks that cause the amount of        carbon dioxide and other greenhouse gases to change naturally        even in the absence of human impact. Climate change throughout        geological history has caused many extinctions. The concern        about the threat of human induced climate change (i.e., global        warming) resulted in the Kyoto Protocol that has been approved        by over 165 countries and is an international agreement that        commits the developed countries to reduce their carbon        emissions.    -   c. One reason global warming is thought by the Intergovernmental        Panel on Climate Change (IPCC) to be a threat is because of the        sea level rise resulting from the melting of glaciers and the        expansion of the ocean as our planet becomes hotter. Hundreds of        millions of people who live just above sea level on islands or        on the coasts are threatened by destructive flooding requiring        relocation or the building of sea walls if the sea level rises        even a meter. There is also a threat to other species from        climate change which will destroy ecosystems that cannot adjust        to the fast rate of human caused climate change. Additional        threats include increased infectious diseases and more extreme        weather as well as direct threats from extreme heat.    -   d. The challenge of dealing with global warming can be        demonstrated using a simple model. Let C_(CA) (Y_(N)) represent        the carbon dioxide added to the atmosphere in year Y_(N) in        gigatonnes per year. Similarly, let C_(EX) (Y_(N)) equal the        amount extracted, C_(EM) (Y_(N)) the amount emitted by humans        and C_(N) (Y_(N)) be the amount either added or removed due to        natural variations in the carbon cycle. Today, the land stores        each year approximately 1.8 gigatonnes (10⁹ tonnes) of carbon        dioxide and the ocean approximately 10.5 gigatonnes (note carbon        dioxide is 3.66 times heavier than carbon), while the amount        humans add by emissions is about 24 gigatonnes of carbon        dioxide. More generally, we have:        C_(CA)(Y_(N))=−C_(EX)(Y_(N))+C_(EM)(Y_(N))+C_(N)(Y_(N))        C_(A)(Y_(N+1))=C_(A)(Y_(N))+C_(CA)(Y_(N))        where C_(A)(Y_(N)) is the amount of carbon in the atmosphere in        year Y_(N), 2780 gigatonnes of carbon dioxide today. Other forms        of carbon contribute to global warming, most notably methane,        although by weight they represent a small component.    -   e. If C_(EX) (Y_(N)) is set to zero then the only way one could        possibly stop adding carbon dioxide to the atmosphere would be        to reduce our emissions to be equal to the natural uptake.        However, C_(N) (Y_(N)) itself varies greatly and can be a net        addition to the atmosphere from the much larger natural carbon        cycle which adds and subtracts carbon at about 750 gigatonnes of        carbon per year. It is the shifts in this natural balance that        has caused climate change before our species existed and will        also continue to do so in the future. Thus, it is clear that        there is no solution that only reduces human contributions to        carbon dioxide emissions that can remove the risk of climate        change. With air extraction and the capability to increase or        decrease the amount of carbon dioxide in the atmosphere one can        in principle compensate for other greenhouse gases like methane        that can change their concentrations and cause climate change.    -   f. Accordingly, there is a broadly recognized need for a system        and method for reducing the amount of carbon dioxide in the        atmosphere created by burning of fossil fuels and for providing        a low cost, non-polluting renewable energy source as a        substitute for fossil fuels.    -   g. Published U.S. patent application Ser. No. 12/124,864        describes several system and method concepts for addressing that        need.

SUMMARY OF THE PRESENT INVENTION

The present invention provides further new and useful system and methodconcepts for removing carbon dioxide from a mass of carbon dioxide ladenair by directing the CO₂ laden air through a sorbent structure thatbinds (captures) CO₂, and removing CO₂ from the sorbent structure (andthereby effectively regenerating the sorbent structure) by using processheat to heat the sorbent structure. In this application, the sorbentstructure preferably comprises an amine that binds CO₂, which is carriedby a substrate, or forms part of a monolithic sorbent structure. Inaddition, in this application, reference to a “mass” (or “flow” or“stream”) of “CO₂ laden air (or carbon dioxide laden air)” means air ata particular location with a concentration of CO₂ that is similar to theconcentration of CO₂ in the atmosphere at that particular location.

In the system and method concepts of published U.S. application Ser. No.12/124,864, carbon dioxide laden air is directed through a substratethat is coated with (or has embedded in it) a sorbent that absorbs orbinds carbon dioxide, to remove the carbon dioxide from the air. Processheat converted into the form of steam or other medium (e.g. gas) isdirected at the sorbent, to separate the carbon dioxide from the sorbent(so the carbon dioxide can be drawn off and sequestered), and toregenerate the sorbent (so that the sorbent can continue to be used toremove carbon dioxide from the air).

In one of its basic aspects, this application provides additionalstructures and techniques for separating carbon dioxide from carbondioxide laden air, and using process heat to separate carbon dioxidefrom a sorbent and regenerate the sorbent that further improves thesystem disclosed in application Ser. No. 12/124,864, and particularlyFIG. 6 of that application.

Moreover, in another of its aspects, this application provides someadditional structures and techniques that can be used to capture carbondioxide from carbon dioxide laden air, and using process heat toseparate carbon dioxide from a sorbent and regenerate the sorbent, in amanner that enables the carbon dioxide separation and regeneration to bepracticed directly in line with a source of flue gases that wouldotherwise emanate directly from that source and direct carbon dioxideladen air into the atmosphere.

These and other features of this invention are described in, or areapparent from, the following detailed description, and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES AND EXHIBITS

FIGS. 1-9 illustrate the system and method concepts described inpublished U.S. application Ser. No. 12/124,864; Specifically,

a. FIG. 1 is a generalized block diagram of a system for removing carbondioxide from an atmosphere according to an exemplary embodiment of theinvention of Ser. No. 12/124,864;

b. FIG. 2 is a block diagram of a system for removing carbon dioxidefrom an atmosphere according to an exemplary embodiment of the inventionof Ser. No. 12/124,864;

c. FIG. 3 is a block diagram of an air extraction system according to anexemplary embodiment of the invention of Ser. No. 12/124,864;

d. FIG. 4 is a map illustrating a global thermostat according to anexemplary embodiment of the invention of Ser. No. 12/124,864;

e. FIG. 5 is a block diagram of a system for removing carbon dioxidefrom an atmosphere according to an exemplary embodiment of the inventionof Ser. No. 12/124,864;

f. FIG. 6 is a schematic illustration of one version of a medium forremoving carbon dioxide from an atmosphere and for removing carbondioxide from the medium, according to the invention of Ser. No.12/124,864;

g. FIG. 7 is a schematic illustration of another version of a medium forremoving carbon dioxide from an atmosphere and for removing carbondioxide from the medium, according to the invention of Ser. No.12/124,864;

h. FIG. 8 is a schematic illustration of still another version of amedium for removing carbon dioxide from an atmosphere and for removingcarbon dioxide from the medium, according to the invention of Ser. No.12/124,864; and

i. FIG. 9 is a schematic illustration of yet another version of a mediumfor removing carbon dioxide from an atmosphere and for removing carbondioxide from the medium, according to the invention of Ser. No.12/124,864.

FIGS. 10 a and 10 b schematically illustrate two versions of a structureand technique for removing carbon dioxide from carbon dioxide laden air,and regenerating the sorbent that absorbs or binds the carbon dioxide,according to the principles of the present invention;

FIGS. 10 c and 10 d are top and side views of one form of elevatorstructure for use in the system and method of FIGS. 10 a and 10 b, inone of its operating positions;

FIGS. 10 e and 10 f are top and side views of the elevator structure ofFIGS. 10 c and 10 d, in another of its operating positions;

FIG. 10 g schematically shows details of structure that can be used tostrip the captured CO₂ and regenerate the sorbent, in accordance withthe principles of the present invention;

FIG. 10 h is a schematic, enlarged illustration of the basic principlesof the elevator structure of the embodiment of FIGS. 10 a and 10 b;

FIGS. 11 a and 11 b schematically illustrate two other versions of astructure and technique for of removing carbon dioxide from carbondioxide laden air, and regenerating the sorbent that absorbs or bindsthe carbon dioxide, according to the principles of the presentinvention;

FIG. 12 is a schematic illustration of a monolithic, sorbent supportstructure, of a type produced by Corning under the trademark Celcor®,that can be used as a sorbent substrate, in accordance with theprinciples of the present invention.

Exhibits A-B are enlarged, color images of FIGS. 10 a-10 b, withnarratives that further describe the structure and operation of theembodiments of FIGS. 10 a-10 b; and

Exhibits C and D are enlarged, color images of FIGS. 11 a, 11 b, withnarratives that further describe the structure and operation of theembodiments of FIGS. 11 a, 11 b.

DETAILED DESCRIPTION Background Description Of The System And MethodConcepts of application Ser. No. 12/124,864

Initially, it is believed useful to describe the method and system ofU.S. application Ser. No. 12/124,864, to provide background for theadditional ways the present invention further develops those principles.FIGS. 1-9 illustrate the system and method of application Ser. No.12/124,864. FIG. 1 is a generalized block diagram of a system, generallydesignated by reference number 1, for removing carbon dioxide from anatmosphere according to an exemplary embodiment of the presentinvention. The system 1 includes an air extraction system 40 and acollection system 50 that isolates the removed carbon dioxide to alocation for at least one of sequestration, storage and generation of arenewable carbon fuel or the generation of a non-fuel product such asfertilizer and construction materials (or to be used in green houses orto enhance the rate of microbial production of biofuels). The airextraction system 40 preferably incorporates any known orlater-discovered CO₂ extraction method, including methods which use amedium (also referred to as a sorbent) to absorb and/or bind (adsorb)CO₂ from the atmospheric air by exposing the medium to chemical,electrical and/or physical interaction with the CO₂ in the captured air.The medium may be liquid, gaseous or solid, or a combination of liquid,gaseous and solid substances, where in the case of solids, the substanceis preferably porous. The medium is preferably recyclable so that afterthe CO₂ is captured by the medium and separated from the medium forsequestration, the medium can be reused for absorption/binding ofadditional CO₂. However, in other embodiments the medium may besequestered along with the captured CO₂. As shown in FIG. 1, theseparation of the CO₂ from the medium, as well as other processes suchas the absorption/binding of CO₂ and the sequestration of the CO₂performed by the sequestration system 50, may be made more efficient bythe addition of heat to the air extraction system 40. In the presentinvention, the heat is process heat generated e.g. by a solar energygenerator, such as a solar collector, to be described in further detailbelow. In other embodiments, process heat may be provided by other typesof energy sources, such as, for example, fossil fuel, geothermal,nuclear, biomass, and other renewable energy sources. The term “processheat” as used herein refers to the lower temperature heat remainingafter the higher temperature heat has been used to generate electricity.More generally, the term “process heat” refers to any low temperatureheat remaining after a primary process or that is added by the processitself, such as, for example, exothermic carbonation reactions in whichcarbon dioxide is stored as a mineral or in fact when it binds to themedium and is captured. Moreover, “process heat” may be provided fromthe use of sources of energy to produce products other than power orelectrical generation. For example, primary processing such as chemicalprocessing, production of cement, steel or aluminum, production ofenergy products like coal to liquid energy products, refining, may useheat to drive the primary processing, and the unused heat remainingafter the primary processing or created during the primary processingwould be the process heat of such processing, and can be used in asystem or method according to the principles of the present invention. Aparticularly preferred way of providing process heat is by aco-generation process, in which a primary process (e.g. for generatingelectricity) provides a source of process heat (either directly in theform of steam, or in a form that can be used to heat a body of liquid toproduce steam) and that process heat is further used in the mannerdescribed herein to remove CO₂ from a substrate and regenerate thesorbent carried by the substrate.

Applicants' preferred concept of extracting carbon dioxide from theatmosphere and using process heat to separate carbon dioxide from thecollection medium is a significant way of addressing the global warmingproblem, and goes against the conventional wisdom in the art (and iscounterintuitive to those in the art). Specifically, the use of processheat to solve the global warming problem by extracting carbon dioxide(CO₂) from the low concentration ambient air is very attractive comparedto both the conventional approach of extracting CO₂ from highconcentration flue gas sources and other schemes known in the art forextracting CO₂ from the ambient atmosphere. In the former case it goesdirectly against conventional wisdom that 300 times lower concentrationof the CO₂ in ambient atmosphere would expect it to be 300 times moreexpensive since separation costs are thought to generally scaleinversely with the concentration. Thus federally funded efforts havebeen directed at extracting CO₂ from the flue gas emissions of powerplants (e.g. clean coal) and experts have publicly claimed that the useof ambient air as opposed to flue gas makes no sense. However, the largeinfinite size of the ambient air source compared to the finite flue gassource and sources generally is one feature that enables applicants'approach to be effective in spite of conventional wisdom and practice.In the flue gas case the emissions containing the CO₂ are at a highertemperature (65-70 degrees centigrade) and therefore regeneration useshigher temperature heat which is more costly than is needed for the coolambient air (approximately 25-30 degrees centigrade). There are otherbenefits of applicants' approach including the ability to use very thinseparation devices that also provide further process improvements. Thus,it could be less costly to remove CO₂ by piping the process heat to aglobal thermostat facility that operates on the principles ofapplicants' invention, rather than cleaning up directly its flueemissions. In addition, the applicants' approach would produce negativecarbon, actually reducing the amount of CO₂ in the atmosphere, whilecleaning up the flue gas would only prevent the CO₂ content in the airfrom increasing.

Further analysis shows that one cannot solve the global warming problemin a timely manner to reduce the great risk it poses by simply cleaningup large stationary fossil fuel sources like coal plants or for thatmatter by conservation or use of renewables. One needs to actually beable, as is the case in this invention, to extract CO₂ from theatmosphere thus reducing the ambient concentration (“negative carbon”)and reducing the threat of global warming. Other published schemes forextracting CO₂ from the ambient atmosphere have used higher temperatureheat generally and not process heat specifically and therefore have notbeen seriously considered because of their high energy costs.

FIG. 2 is a block diagram of a system, generally designated by referencenumber 2, for removing carbon dioxide from an atmosphere according to anexemplary embodiment of the present invention. The system 2 includes asolar collector 10, an optional supplemental energy source 20, a powergenerator 30, an air extraction system 42 and a collection system 50.Each of these components of the system 1 are explained in detail below.

The solar collector 10 may be any known or future-discovered solarenergy collection system, which may include solar energy collectionunits, such as, for example, concentrated solar power parabolic mirrors,and concentrated solar power towers. As is known in the art, the solarcollector 10 converts solar energy to thermal energy, which may be usedto drive the power generator 30. Residual thermal energy (i.e., processheat) may be used to drive the air extraction system 42 and/or thecollection system 50. For example, the process heat may be used toimprove the efficiency of chemical and/or physical reactions used in theair extraction system 42 to absorb CO₂ from the air and/or to drive offthe CO₂ from the medium. In addition, in other exemplary embodiments, asshown by the dashed arrows in FIG. 2, direct heat from the solarcollector 10 may be used to drive the air extraction system 42 and/orthe collection system 50.

The power generator 30 may be, for example, a thermal power generatorthat converts the thermal energy provided by the solar collector toelectricity. As is known in the art, the sun's heat may be focused on amedium, such as molten salts, that is then used to generate hightemperature, high pressure steam that drives a turbine to generateelectricity. The generated electricity may then be used to power theother components of the system 2, in addition to providing power to thegeneral population as part of a power grid. In this regard, the thermalenergy provided by the solar collector 10 may be supplemented by energygenerated by the supplemental energy source 20. For example, thesupplemental energy source 20 may be a waste incineration plant, whichprovides additional thermal energy to drive the power generator 30.Also, it should be appreciated that any other type of renewable energysource may be used in addition to solar energy, and preferably arenewable energy source that produces heat as a precursor to thegeneration of electricity. Other potential renewable energy sources tobe used in addition to solar energy include, for example, nuclear,biomass, and geothermal energy sources.

Alternatively, the power generator 30 may be any known or laterdiscovered fossil fuel facility (plant) that relies on the burning offossil fuels, such as, for example, coal, fuel oil, natural gas and oilshale, for the generation of electricity. The power generator may alsobe for a purpose other than generating electricity (for example thepower generator could be for chemical processing, or various otherpurposes like producing aluminum). The thermal energy produced by thefossil fuel power plant 30 is used to produce electricity and theresidual thermal energy (i.e., process heat) may be used to drive theair extraction system 42 and/or the sequestration system 50. Forexample, the process heat from the fossil fuel power plant 30 may beused to improve the efficiency of chemical and/or physical reactionsused in the air extraction system 42 to absorb/bind CO₂ from the airand/or to drive off the CO₂ from the medium. The process heat providedby the fossil fuel power plant 30 may be supplemented by energygenerated by a supplemental energy source. For example, the supplementalenergy source may be a waste incineration plant or a renewable energysource, such as, for example, solar, nuclear, biomass, and geothermalenergy sources, which provides additional thermal energy to drive theair extraction system 42 and/or the collection system 50. Process heatfrom the supplemental energy source may also be used to drive the airextraction system 42 and/or the collection system 50.

Moreover, as described above, “process heat” may be provided from theuse of sources of energy to produce products other than power orelectrical generation. For example, in a co-generation system, primaryprocessing such as chemical processing, production of cement, steel oraluminum, refining, production of energy products like coal and liquidenergy products, may use heat to drive the primary processing, and theunused heat remaining after the primary processing or created during theprimary processing would be the process heat of such processing, and canbe used in a system or method according to the principles of the presentinvention. When the primary processing is for generating electricity,the process heat is produced in the form of steam (or in a form that canheat a body of fluid to produce steam), and that steam is used in themanner described herein to remove CO₂ from a substrate and regeneratethe sorbent carried by the substrate.

FIG. 3 is a block diagram of the air extractor system 42 useable withthe system 2 according to an exemplary embodiment of the presentinvention. The air extractor system 42 includes an air contactor 41, acausticizer 43, a slaker 45, a calciner 47 and a capture unit 49. Theair contactor 41 may use a sorbent material to selectively capture CO₂from the air, and may be composed of any known or later-discoveredcontactor structures, such as, for example, large convection towers,open, stagnant pools, and packed scrubbing towers. In the presentembodiment, the sorbent material which readily absorbs/binds CO₂ fromthe air may be an amine that can operate (e.g. capture CO₂, and beprocessed to collect the CO₂ and regenerate the sorbent) at relativelylow temperature (e.g. below about 120 degrees C.) or sodium hydroxide(NaOH) which would operate at significantly higher temperature. Itshould be appreciated that other known or future-discovered capturemethods may be used, such as, for example, chemical absorption, physicaland chemical adsorption, low-temperature distillation, gas-separationmembranes, mineralization/biomineralization and vegetation. As a furtherexample, as known in the art, aqueous amine solutions or amine enrichedsolid sorbents may be used to absorb/bind CO₂. Preferably, the sorbentmaterial is regenerated and the capture method requires less than about100-120° C. heat to regenerate the sorbent material. Thus, the preferredsorbent material is an amine. It should also be noted that futureimproved sorbents with the ability to be regenerated with lowtemperature heat could also be used. Moreover, a sorbent such as NAOH(because of its need for high temperature) would only be useable in aco-generation mode of this invention for processes that have highertemperature process heat available after completing the primary processfor which the heat is generated, e.g. steel manufacturing. However,because at this time this heat is much less available, and more costly,its use could limit the full scope of this invention to the effect thatit might not adequately address climate change, and the use of NAOH as asorbent is therefore not preferred at this time.

The capture unit 49 captures the CO₂ driven off at the calciner 47 usingany know or later-discovered CO₂ capturing method that is effective inthe low concentrations in which CO₂ is present in the atmosphere andthat needs only low temperature heat for regeneration. For example, thecapture unit 49 may use an amine based capture system, such as thesystem described in Gray et al U.S. Pat. No. 6,547,854, dated Apr. 15,2003, and also Sirwardane U.S. Pat. No. 6,908,497, dated Jun. 21, 2005,both of which are incorporated herein by reference. The capture unit 49may also compress the captured CO₂ to liquid form so that the CO₂ may bemore easily sequestered.

The collection system 50 isolates the removed carbon dioxide to alocation for at least one of sequestration, storage and generation of arenewable carbon fuel or the generation of a non-fuel product such asfertilizer and construction materials. The collection system 50 may useany known or future-discovered carbon, sequestration and/or storingtechniques, such as, for example, injection into geologic formations ormineral sequestration. In the case of injection, the captured CO₂ may besequestered in geologic formations such as, for example, oil and gasreservoirs, unmineable coal seams and deep saline reservoirs. In thisregard, in many cases, injection of CO₂ into a geologic formation mayenhance the recovery of hydrocarbons, providing the value-addedbyproducts that can offset the cost of CO₂ capture and collection. Forexample, injection of CO₂ into an oil or natural gas reservoir pushesout the product in a process known as enhanced oil recovery. Thecaptured CO₂ may be sequestered underground, and according to at leastone embodiment of the invention at a remote site upwind from the othercomponents of the system 2 so that any leakage from the site isrecaptured by the system 2.

In regards to mineral sequestration, CO₂ may be sequestered by acarbonation reaction with calcium and magnesium silicates, which occurnaturally as mineral deposits. For example, as shown in reactions (1)and (2) below, CO₂ may be reacted with forsterite and serpentine, whichproduces solid calcium and magnesium carbonates in an exothermicreaction.1/2Mg₂SiO₄+CO₂=MgCO₃+1/2SiO₂+95 kJ/mole  (1)1/3Mg₃Si₂O₅(OH)₄+CO₂=MgCO₃+2/3SiO₂+2/3H₂O+64 kJ/mole  (2)

Both of these reactions are favored at low temperatures, which favor anamine as the sorbent. In this regard, both the air capture and airsequestration processes described herein may use electricity and/orthermal energy generated by the solar collector 10 (or other renewableenergy source) to drive the necessary reactions and power theappropriate system components. In an exemplary embodiment of the presentinvention, a high temperature carrier may be heated up to a temperaturein a range of about 400° C. to about 500° C. to generate steam to run agenerator for electricity, and the lower temperature and pressure steamthat exits from the electrical generating turbines can be used to driveoff the CO₂ and regenerate the sorbent (e.g., an amine at lowtemperatures or NaOH at higher temperatures). The temperature of thehigh temperature heat, the generated electricity and the temperature ofthe lower temperature process heat remaining after electricityproduction can be adjusted to produce the mix of electricity productionand CO₂ removal that is considered optimal for a given co-generationapplication. In addition, in exemplary embodiments, still lowertemperature process heat that emerges out of the capture andsequestration steps may be used to cool equipment used in these steps.

One or more systems for removing carbon dioxide from an atmosphere maybe used as part of a global thermostat according to an exemplaryembodiment of the present invention. By regulating the amount of carbondioxide in the atmosphere and hence the greenhouse effect caused bycarbon dioxide and other gas emissions, the system described herein maybe used to alter the global average temperature. According to at leastone exemplary embodiment of the present invention, several carbondioxide capture and sequestration systems may be located at differentlocations across the globe so that operation of the multiple systems maybe used to alter the CO₂ concentration in the atmosphere and thus changethe greenhouse gas heating of the planet. Locations may be chosen so asto have the most effect on areas such as large industrial centers andhighly populated cities, or natural point sources of CO₂ each of whichcould create locally higher concentrations of CO₂ that would enable morecost efficient capture. For example, as shown in FIG. 4, multiplesystems 1 may be scattered across the globe, and internationalcooperation, including, for example, international funding andagreements, may be used to regulate the construction and control of thesystems 1. In this regard, greenhouse gases concentration can be changedto alter the average global temperature of the planet to avoid coolingand warming periods, which can be destructive to human and ecologicalsystems. During the past history of our planet, for example, there havebeen many periods of glaciation and rapid temperature swings that havecaused destruction and even mass extinctions. Such temperature swings inthe future could be a direct cause of massive damage and destabilizationof human society from conflicts resulting from potential diminishedresources. The global thermostat described herein may be the key topreventing such disasters in the decades to come.

FIG. 5 is a block diagram of a system, generally designated by referencenumber 100, for removing carbon dioxide from an atmosphere according toanother exemplary embodiment of the present invention. The system 100includes a renewable energy source 110, an optional supplemental energysource 120, a power generator 130, an air extraction system 142 and acollection system 150. The present embodiment differs from theembodiment of FIG. 2 in that the renewable energy source 110 may be anyknown or future-discovered energy source besides solar, such as, forexample, nuclear, geothermal, and biomass energy sources. Preferably,the renewal energy source produces thermal energy, which can be used toproduce electricity and to improve the efficiency of the variouschemical and/or physical reactions that take place within the airextraction system 142 and the collection system 150. In this regard, theair extraction system 142 and the collection system 150 may be the sameas described with reference to the previous embodiment, or may includecomponents according to any other known or future-discovered airextraction and collection systems. In addition, as shown in FIG. 4 withreference to the previous embodiment, a plurality of systems 100 may bestrategically placed across the globe, and control of the systems 100may be coordinated so as to collectively function as a globalthermostat.

FIGS. 6-9 are schematic illustrations of several ways that carbondioxide can be removed from an atmosphere, according to the principlesof the present invention.

Specifically, in FIG. 6, a pair of substrates 600, 602 are illustrated,each of which has a medium (e.g. NAOH, an amine or other suitablesorbent) that can be brought into contact with an atmosphere to removecarbon dioxide from the atmosphere. The substrates 600, 602 are pancakeshaped (in the sense that they are relatively large area compared totheir thickness) oriented vertically, and can each be relatively large(in surface area) and relatively thin (e.g. on the order of a fewmillimeters, and preferably not thicker than a meter). Each substratecan move (e.g. by a pulley or hydraulic system, not shown) between anupper position in which carbon dioxide laden air is brought into contactwith the medium carried by the substrate to remove carbon dioxide fromthe air, and a lower position in which process heat is directed at thesubstrate to remove carbon dioxide from the medium. The substrates 600,602 are porous with large surface areas, so that air directed at asubstrate can flow through the substrate. When a substrate is in anupper position (e.g. the position of substrate 600), carbon dioxideladen air is directed at the substrate (e.g. by a fan 604 shown indashed lines), so that as the air flows through the substrate, thecarbon dioxide contacts the medium and is substantially removed from theair. Thus, carbon dioxide laden air is directed at and through thesubstrate so that carbon dioxide comes into contact with the medium,carbon dioxide is substantially removed from the air by the medium, andair from which the carbon dioxide has been substantially removed isdirected away from the substrate. When a substrate is moved to the lowerposition (e.g. the position of substrate 602), process heat is directedat the substrate (e.g. via a fluid conduit 606), and carbon dioxide isremoved (drawn off) by a source of fluid that is directed at thesubstrate (in the direction shown by arrow 608) and a source of suction610 by which carbon dioxide that has been removed from the medium isdrawn away from the substrate. The substrates 600, 602 can alternativelymove between the upper and lower positions, so that the substrate in theupper position is removing carbon dioxide from the air and carbondioxide is being removed from the substrate in the lower position. Itshould be noted that rather than the fan, if there are strong windsavailable natural wind flows can be used to drive the air through thesubstrate. In addition, as described below, the fan can be replaced witha solar driven source (or by either wind or thermally-driven aircurrents), in which case the efficiency and cost reduction of extractionof carbon dioxide from atmospheric air can be further improved.Moreover, rather than switching the positions of the substrates, themeans for generating the air flows, the flow of process heat, and theflow of carbon dioxide away from the substrate can be switched as carbondioxide is captured from the air and then extracted from the medium, aswill be readily apparent to those in the art.

FIG. 7 is a schematic illustration of another version of a medium forremoving carbon dioxide from an atmosphere and for removing carbondioxide from the medium, according to the principles of the presentinvention. Specifically, in FIG. 7, a pair of substrates 700, 702 areillustrated, each of which has a medium (e.g. NAOH, an amine or othersuitable sorbent) that can be brought into contact with an atmosphere toremove carbon dioxide from the atmosphere. The substrates 700, 702 areoriented horizontally, and can each be relatively large (in surfacearea) and relatively thin (e.g. on the order of millimeters orcentimeters, up to a meter). Each substrate can move horizontally (e.g.by a pulley system (not shown) between an air extraction position inwhich carbon dioxide laden air is brought into contact with the mediumcarried by the substrate to remove carbon dioxide from the air, and acarbon extraction position in which process heat is directed at thesubstrate to remove carbon dioxide from the medium. The substrates 700,702 are porous, so that air directed at a substrate can flow through thesubstrate. When a substrate is in an air extraction position (e.g. theposition of substrate 700), carbon dioxide laden air is directed at thesubstrate (e.g. by a fan 704 shown in dashed lines), so that as the airflows through the substrate, the carbon dioxide contacts the medium andis substantially removed from the air. Thus, carbon dioxide laden air isdirected at and through the substrate so that carbon dioxide comes intocontact with the medium, carbon dioxide is substantially removed fromthe air by the medium, and air from which the carbon dioxide has beensubstantially removed is directed away from the substrate. When asubstrate is moved to the carbon extraction position (e.g. the positionof substrate 702), process heat is directed at the substrate (e.g. via afluid conduit 706), and carbon dioxide is removed (drawn off) by asource of fluid that is directed at the substrate (in the directionshown by arrow 708) and a source of suction 710 by which carbon dioxidethat has been removed from the medium is drawn away from the substrate.The substrates 700, 702 can alternatively move between the airextraction and carbon extraction positions, so that the substrate in theair extraction position is removing carbon dioxide from the air andcarbon dioxide is being removed from the substrate in the carbonextraction position. It should be noted that rather than the fan, ifthere are strong winds available natural wind flows can be used to drivethe air through the substrate. In addition, as described below, the fancan be replaced with a solar driven source (or by either wind orthermally-driven air currents), in which case the efficiency and costreduction of extraction of carbon dioxide from atmospheric air can befurther improved. Moreover, rather than switching the positions of thesubstrates, the means for generating the air flows, the flow of processheat, and the flow of carbon dioxide away from the substrate can beswitched as carbon dioxide is captured from the air and then extractedfrom the medium, as will be readily apparent to those in the art.

The version of the invention shown in FIG. 9 is generally similar to thehorizontally oriented version of FIG. 7, but in the version of FIG. 9,rather than a fan being the source that moves the carbon laden airthrough the substrate in the air extraction position (e.g. substrate900), there is a source of gas flow that is generated from a solarheating tower or chimney (shown schematically at 912 in FIG. 9). A solarchimney can be generated by heating an air mass with the sun. The solarchimney would have a “skirt” (shown in dashed lines 913 in FIG. 9) thatenables the solar heated air to be concentrated in the chimney. Thus, asolar field with a solar chimney can be associated with a system andstructure that removes carbon dioxide from the atmosphere and removescarbon dioxide from a medium in the manner shown and described inconnection with FIG. 7. However, rather than a fan 704 as the primarydriver of carbon dioxide laden air at the substrate, the carbon dioxideladen air is heated by solar energy and that air is allowed to rise inthe solar funnel or tower 912. Because of the tendency for the hot airto rise, an upward draft is generated, that would carry with it carbondioxide laden air, and the substrate 900 would be positioned in the wayof that upward draft. Thus, the carbon dioxide laden air would bedirected through the substrate 900 in the air extraction position, andcarbon dioxide would be removed from the substrate 902 in the carbonextraction position in the same way as shown and described in connectionwith FIG. 7. By driving the extraction of carbon dioxide from air bysolar energy, the costs of extraction are further reduced, and theoverall operation is highly renewable. Of course, provision would needto be made for those periods when the sun didn't shine, and some form ofdriver similar to the fan 704 (FIG. 7) would be needed. But in any case,having periods in which, instead of the fan, replacing the fan with asolar driven source (or by either wind or thermally-driven aircurrents), the efficiency and cost reduction of extraction of carbondioxide from atmospheric air can be further improved.

FIG. 8 is a schematic illustration of yet another version of a mediumfor removing carbon dioxide from an atmosphere and for removing carbondioxide from the medium, according to the principles of the presentinvention. In FIG. 8, the medium from which carbon dioxide is removedfrom atmospheric air and from which carbon dioxide is removed from themedium is disposed on a continuously moving substrate composed, e.g., ofpellets laden with the sorbent 800. The substrate moves through an airextraction zone 814, where carbon dioxide laden air is directed at andthrough the substrate (which is also porous as with the priorembodiments) so that carbon dioxide is removed from the air. Thesubstrate 800 then moves to a carbon extraction zone 816, where processheat is directed at the substrate and carbon is drawn away from thesubstrate in the manner described above in connection with FIGS. 6, 7.Then, the substrate 800 moves to and through a heat exchange zone 818where the temperature of the substrate is lowered (e.g. by the air thatflowed through the substrate in the air extraction zone, and by anyadditional cooling device that may be useful in reducing the temperatureof the substrate to a level that enables it to efficiently remove carbondioxide from the air when the substrate moves back through theextraction zone 814. In addition, the system of FIG. 8 may have anothercarbon extraction zone 816, where process heat is directed at thesubstrate and carbon is drawn away from the substrate in the mannerdescribed above in connection with FIGS. 6, 7.

It should also be noted that in all of the versions of the inventiondescribed above, the removal of carbon dioxide from the air can be atleast partially performed under non equilibrium conditions.Additionally, it should be noted that applicants' preferred concept forextracting carbon dioxide from the atmosphere comprises using arelatively thin, large surface area substrate with a medium (e.g. anamine) that removes carbon dioxide from the atmosphere and using processheat to remove carbon dioxide from the medium. Using a relatively largearea substrate perpendicular to the direction of air flow isparticularly useful, because of the relatively low concentration ofcarbon dioxide in the atmosphere (as opposed to the relatively highconcentration that would normally be found, e.g. in flue gases).

New System, Components and Method Concepts for Removing Carbon Dioxidefrom Carbon Dioxide Laden Air, According to the Present InventionSorbent Structure and General Operation of Sorbent

FIG. 12 is a schematic illustration of a cellular, ceramic substratestructure, of a type produced by Corning under the trademark Celcor®,that can be used in a sorbent structure, in accordance with theprinciples of the present invention. The sorbent (e.g. an amine) iscarried by (e.g. coated or otherwise immobilized on) the inside of oneor more of the Celcor®, cellular ceramic substrates, which provides ahigh surface area and low pressure drop, as CO₂ laden air flows throughthe substrate. The sorbent structure can comprise, e.g., a plurality ofthe Celcor,® cellular, ceramic substrates or a single substrate, havingthe type of pancake shape described above in connection with FIG. 6(i.e. surface area much greater than thickness), and the CO₂ laden airis directed through the cells of the sorbent structure. It is alsocontemplated that the sorbent structure can be formed by embedding thesorbent material in the Celcor® cellular, ceramic structure to form amonolithic sorbent structure.

In addition, it should be noted that the substrate, while preferablyceramic, an inorganic material, can be an organic material.

CO₂ laden air is passed through the sorbent structure, which ispreferably pancake shaped, and the sorbent structure binds the CO₂ untilthe sorbent structure reaches a specified saturation level, or the CO₂level at the exit of the sorbent structure reaches a specified valuedenoting that CO₂ breakthrough has started (CO₂ breakthrough means thatthe sorbent structure is saturated enough with CO₂ that a significantamount of additional CO₂ is not being captured by the sorbentstructure).

When it is desired to remove and collect CO₂ from the sorbent structure(and regenerate the sorbent structure), in a manner described furtherbelow in connection with FIGS. 10 a-h, the sorbent structure is removedfrom the carbon dioxide laden air stream and isolated from the airstream and from other sources of air ingress. Steam is then passedthrough the sorbent structure. The steam will initially condense andtransfer its latent heat of condensation to the sorbent structure.Eventually the sorbent structure will reach saturation temperature andthe steam will pass through the sorbent structure without condensing. Asthe condensate and then the steam pass through and heat the sorbentstructure the CO₂ that was captured by the sorbent structure will beliberated from the sorbent structure producing more condensed water inproviding the needed heat of reaction to liberate the CO₂ from thesorbent structure and be pushed out of the sorbent structure by thesteam or extracted by a fan/pump. Thus, the steam that is passed throughthe sorbent structure and releases the CO₂ from the sorbent, and forenergy efficiency cost reasons one would want to minimize the amount ofsteam used and that is mixed in with the CO₂. Thus, whatever is (or canbe) condensed upon exiting the regeneration chamber and the condensatecan be added to that generated in the regeneration chamber, and recycledto be heat and converted back into steam for use. This technique isreferred to as “steam stripping” and is also described further below.

Vertical Elevator Concept of FIGS. 10 a-10 f, and 10 h

FIGS. 10 a, 10 b are schematic illustrations of structure and methodconcepts that further develop the principles by which carbon dioxide canbe removed from CO₂ laden air, according to the principles of thepresent invention. In particular, FIGS. 10 a, 10 b further develop theprinciples disclosed in FIG. 6 of U.S. application Ser. No. 12/124,864.FIGS. 10 c-hfurther show details of the structure and method of FIGS. 10a and 10 b.

Specifically, in FIG. 10 a, a rectangular carbon dioxide capturestructure 1000 is illustrated, which has a sorbent structure, asdescribed herein, that can be brought into contact with CO₂ laden air toremove carbon dioxide from the CO₂ laden air. The rectangular carbondioxide capture structure is similar to the pancake shaped substrates ofFIG. 6 in the sense that it has relatively large area compared to itsthickness, and is oriented vertically in relation to a flow of CO₂ ladenair. The carbon dioxide capture structure 1000 comprises a top member1002 that is preferably a solid metal plate, and a sorbent structure1004 depending from the top member 1002. When located in a stream of CO₂laden air, the sorbent structure 1004 is open to CO₂ laden air stream onthe large area faces through which the air is directed by the fan orprevailing wind and carries the sorbent that binds to carbon dioxideflowing through the sorbent structure, to capture carbon dioxide from aflow of carbon dioxide laden air that is directed through the sorbentstructure. The sorbent structure 1004 provides a high surface area andlow pressure drop, as CO₂ laden air flows through the sorbent structure1004.

The carbon dioxide capture structure 1000 is supported for verticalmovement by an elevator structure, shown and described in overview inconnection with FIGS. 10 a and 10 b, and whose details are furtherdescribed and shown in connection with FIGS. 10 c-f and 10 h. As shownin FIG. 10 a, a hydraulic cylinder 1006 is connected with the top member1002 and is moveable in a structural frame 1008 that protects thehydraulic cylinder from the ambient environment. The hydraulic cylinder1006 can selectively move the carbon dioxide capture structure 1000between a carbon dioxide capture position that is in line with a flow ofcarbon dioxide laden air, and a regeneration position described furtherbelow. In the carbon dioxide capture position a flow of carbon dioxideladen air (labeled “fresh air inlet” in FIG. 10 a) is drawn through thecarbon dioxide capture structure 1000 (e.g. by means of an induced draftcreated by a fan 1010 driven by a motor 1012). The carbon dioxide ladenair flows through the sorbent support structure 1004 where the sorbentbinds the carbon dioxide, to remove the carbon dioxide from the air, sothat the air that exits the carbon dioxide capture structure 1000 issubstantially depleted of carbon dioxide (preferably about 95% depletedof carbon dioxide).

The carbon dioxide capture structure 1000 can be selectively moved to aregeneration position (by the hydraulic cylinder 1006 or by a pulleysystem that would perform the analogous function of moving the carbondioxide capture structure between the adsorption and regenerationpositions), where carbon dioxide is separated from the sorbent structure1004, to enable the carbon dioxide to be collected and sequestered, andto enable the sorbent structure to be regenerated, so that the sorbentstructure can then be moved back to a position where it is in line witha flow of carbon dioxide laden air, to remove additional carbon dioxidefrom that air. A regeneration box 1014 is located below the carbondioxide capture structure 1000. The regeneration box 1014 is preferablysolid metal plate on 5 sides, and is open on top, so that when thecarbon dioxide capture structure 1000 is lowered into the box 1014, thetop plate 1002 will close the top of the regeneration box 1014. Theregeneration box 1014 is well insulated for heat conservation purposesand can be selective heated by a flow of process heat (preferably from aco-generation system and process, as described further herein). As theregeneration box 1014 is heated (preferably by the “steam strippingprocess described herein), the carbon dioxide is separated from thesorbent structure, and is drawn off so that the carbon dioxide can besequestered. As the carbon dioxide is separated from the sorbentstructure, and drawn from the regeneration box 1014, the sorbentstructure is regenerated, so that the carbon dioxide capture structure1000 can be moved to the position in which it is in line with a flow ofcarbon dioxide laden air, to remove carbon dioxide from the carbondioxide laden air.

FIG. 10 b schematically illustrates an alternative to the structure andtechnique of FIG. 10 a, in that a pair of carbon dioxide capturestructures 1000 are provided, each of which is configured in accordancewith the carbon dioxide capture structure of FIG. 10 a, and each ofwhich is moved by a hydraulic cylinder 1002 between a carbon captureposition in which the carbon capture structure is in line with a flow ofcarbon laden air, and a regeneration position in which the carbondioxide capture structure is lowered into a regeneration box 1014 thatis configured like, and operates in a similar manner to, theregeneration box 1014 of FIG. 10 a. The only essential different betweenthe carbon capture structure and technique of FIG. 10 b and FIG. 10 b,is that in FIG. 10 b, one carbon dioxide capture structure can always bein line with a flow of carbon dioxide laden air while the other carbondioxide capture structure is being regenerated in the manner describedabove in connection with FIG. 10 a. Thus, in FIG. 10 b (and in a mannersimilar to that shown in FIG. 6), when a carbon dioxide capturestructure 1000 is in an upper position (e.g. the upper position shown inFIG. 10 b), carbon dioxide laden air is directed through a sorbentstructure, so that the sorbent structure binds carbon dioxide in thecarbon dioxide laden air. When a carbon dioxide capture structure 1000is moved to the lower position and into the regeneration box 1014,process heat is directed at the substrate, and carbon dioxide is removed(drawn off) the sorbent support structure (again preferably by the“steam stripping” process described herein). The pair of carbon dioxidecapture structures 1000 can alternatively move between the upper andlower positions, so that the carbon dioxide capture structure in theupper position is removing carbon dioxide from the carbon dioxide ladenair and carbon dioxide is being removed from the sorbent structure thatis in the lower position.

While FIGS. 10 a and 10 b each shows a single sorbent structure forremoving carbon dioxide from carbon dioxide laden air and forregenerating a carbon dioxide sorbent structure (such sorbent structuresometimes referred to herein as a Unit, in practice a global thermostatsystem would have a number of Units, each of which is configured andoperates in accordance with the structures and techniques describedabove, as will be clear to those in the art. Moreover, FIG. 10 h showsand describes the elevator structure in additional detail, and as shownin FIGS. 10 c, d, e and f, the elevator structure can comprise, e.g.,pairs of hydraulic cylinders that are located such that they do notinterfere with the flow of carbon dioxide laden air through the sorbentstructure.

Moreover, the following additional features of the structures andtechniques of FIGS. 10 a and 10 b should also be noted.

-   -   a. Piping, valves, etc. for the Low Level Process Heat        Source/Supply Header (typically Low Pressure Steam), which will        most likely be a horizontal pipe rack run located underneath the        horizontal row of identical Global Thermostat (GT) Units,        running parallel with the “Dimension W” shown in FIGS. 10 a, 10        b . If the number of Global Thermostat (GT) Units is also        expanded vertically upward, by building a structure with        additional platform levels at the appropriate elevations, there        will also be a vertical header, or vertical pipe rack run,        located at the very end of the horizontal row of identical GT        Units, adjacent to the structure containing the additional        platform levels at the appropriate elevations.    -   b. Piping, valves, etc. for the Low Level Process Heat Return        Header (typically Low Pressure Steam Condensate), which will        most likely be a horizontal pipe rack run located underneath the        horizontal row of identical Global Thermostat (GT) Units,        running parallel with the “Dimension W” shown in FIGS. 10 a, 10        b . If the number of Global Thermostat (GT) Units is also        expanded vertically upward, by building a structure with        additional platform levels at the appropriate elevations, there        will also be a vertical header, or vertical pipe rack run,        located at the very end of the horizontal row of identical GT        Units, adjacent to the structure containing the additional        platform levels at the appropriate elevations.    -   c. Piping, valves, etc. for the optional Cooling Water Supply        (CWS) Header, which will most likely be a horizontal pipe rack        run located underneath the horizontal row of identical Global        Thermostat (GT) Units, running parallel with the “Dimension W”        shown in FIGS. 10 a, 10 b . If the number of Global Thermostat        (GT) Units is also expanded vertically upward, by building a        structure with additional platform levels at the appropriate        elevations, there will also be a vertical header, or vertical        pipe rack run, located at the very end of the horizontal row of        identical GT Units, adjacent to the structure containing the        additional platform levels at the appropriate elevations.    -   d. Piping, valves, etc. for the optional Cooling Water Return        (CWR) Header, which will most likely be a horizontal pipe rack        run located underneath the horizontal row of identical Global        Thermostat (GT) Units, running parallel with the “Dimension W”        shown in FIGS. 10 a, 10 b . If the number of Global Thermostat        (GT) Units is also expanded vertically upward, by building a        structure with additional platform levels at the appropriate        elevations, there will also be a vertical header, or vertical        pipe rack run, located at the very end of the horizontal row of        identical GT Units, adjacent to the structure containing the        additional platform levels at the appropriate elevations.    -   e. Piping, valves, etc. for the CO₂ (>95.00 mole %) to CO₂        Product Storage Header, which will most likely be a horizontal        pipe rack run located underneath the horizontal row of identical        Global Thermostat (GT) Units, running parallel with the        “Dimension W” shown in FIGS. 10 a, 10 b. If the number of Global        Thermostat (GT) Units is also expanded vertically upward, by        building a structure with additional platform levels at the        appropriate elevations, there will also be a vertical header, or        vertical pipe rack run, located at the very end of the        horizontal row of identical GT Units, adjacent to the structure        containing the additional platform levels at the appropriate        elevations.    -   f. The CO₂ Receiving/Storage Vessel, and any and all equipment        required to connect to, or tie-in to, a high pressure CO₂        disposal pipeline.    -   g. Supply and Return tie-ins (piping, valves, etc.) to the Low        Level Process Heat Source at the existing industrial facility        (Power Plant, Chemical Plant, or Refinery, etc.), which would        most likely be ordinary low pressure steam supply/low pressure        steam condensate return.    -   h. Supply and Return tie-ins (piping, valves, etc.) to the Low        Level Cooling Source at the existing industrial facility (Power        Plant, Chemical Plant, or Refinery, etc.), which would most        likely be ordinary or common cooling water supply (CWS)/cooling        water return (CWR).    -   i. All instrumentation, all electrical facilities (such as        substations, wiring, etc.), all general utility connections        (such as instrument air, potable water, etc.), all safety and        shutdown systems, etc. This would also include a Control House,        with a typical Computer Data Logger/Computer Control System.    -   j. All of the block valves shown in FIGS. 10 a, 10 b will be        specified to be either “minimal leakage” or TSO (tight shut-off)        block valves, whichever is most practical or most feasible.    -   k. All of the block valves shown in FIGS. 10 a, 10 b will be        fully automated block valves (either motorized, hydraulically,        or pneumatically operated). All of these block valves will be        interlocked together by a timer/sequencer system that is        computer controlled. The Hydraulic Fluid Pump(s) and the CO₂        Product/Recycle Gas Blower(s) will also be connected to, and        interlocked by, the timer/sequencer system that is computer        controlled.    -   l. While the preferred sorbent structure described herein        comprises a sorbent material (i.e. an amine) that is carried by        (e.g. coated or otherwise immobilized on) the inside of Celcor®        cellular substrate, it is contemplated that the sorbent        structure can also be formed by embedding the sorbent material        in the Celcor® cellular structure to form a monolithic sorbent        structure.    -   m. It is recognized that it may be important to remove oxygen        from the environment about the sorbent structure, both before        and after regeneration of the sorbent structure, to avoid oxygen        contamination of the sorbent structure (which would result from        oxygen poisoning the sorbent structure by oxidizing the sorbent        structure). The manner in which removal of oxygen can be handled        is described below in connection with a technique referred to as        “steam stripping with purge gas”.

Steam Stripping

There are 2 techniques that are contemplated for the steam strippingprocess. One technique is referred to as “steam stripping with steamonly”. The other technique is referred to as “steam stripping with purgegas”. Both techniques utilize system components and process steps thatare schematically shown in FIG. 10 g.

The technique referred to as “steam stripping with steam only” works inthe following way:

-   -   a. Air is passed through the channels in the sorbent structure        and the CO₂ is removed from the air by the sorbent structure        until the sorbent structure reaches a specified saturation level        or the CO₂ level at the exit of the sorbent structure reaches a        specified value denoting that CO₂ breakthrough has started, or        for a specified time period determined by testing.    -   b. The sorbent structure is removed from the air stream and        isolated from the air flow and from air ingress and CO₂        migration to the outside air.    -   c. Low pressure steam is passed through the channels in the        sorbent structure. The steam will initially condense and        transfer its latent heat of condensation to the sorbent        structure in the front part of the sorbent structure. The heat        of condensation raises the temperature of the sorbent structure        and provides energy to drive the CO₂ desorption process from the        sorbent structure. Eventually the front part of the sorbent        structure will reach saturation temperature and the liberated        CO₂ will be pushed out by the steam or extracted by a fan. This        process will move deeper into the sorbent structure from the        front part of the sorbent structure where the steam enters until        the CO₂ is liberated (note the fraction released will depend        upon the sorbent structure and temperature steam used). Only an        adequate amount of steam will be provided to achieve desorption        of the CO₂ from the sorbent structure so as to minimize the        steam used and minimize the amount of steam mixed in with the        liberated CO₂). As the condensate and then the steam pass        through the sorbent structure and heat the sorbent the CO₂ will        be liberated from the sorbent structure and be transferred into        the steam and condensate. The condensate will have a limited        ability to “hold” the CO₂ and once saturated the “sour” water        will not hold any more CO₂ and the CO₂ will remain in the vapor        phase as it is pushed out by the steam or extracted with a fan.        Once the steam has passed through the sorbent structure it has        to be condensed to liberate the CO₂. This is achieved in the        condenser which uses cooling water to remove the heat. The        collected stream will have some steam mixed in that will be        minimized to the extent possible, and that steam has to be        condensed to separate it from the CO₂. Alternatively the steam        could be condensed, using heat loss to the atmosphere, in an        uninsulated pipe or a finned pipe. This heat is a loss to the        system although an alternative would be to use the air exiting        the sorbent structure in the adsorption step (Step 1 above) to        condense the steam. This would raise the temperature of the air        at the exit of the sorbent structure and provide an additional        driving force to move the air through the sorbent structure and        reduce the energy requirements.    -   d. Once the sorbent structure has had the CO₂ removed then the        sorbent structure is raised up back into the air stream. The air        will cool the sorbent structure and remove any remaining        moisture. The sorbent structure will then remove the CO₂ until        the specified breakthrough occurs (see Step 1) and the sorbent        structure is then lowered into the regeneration position and the        process repeated.    -   e. The condensate from the desorption process (removing the CO₂        from the sorbent structure) contains CO₂ at saturation levels.        This condensate will be close to saturation temperature (as only        sufficient steam is added to the system to achieve CO₂ removal)        and is recycled to a boiler where low pressure steam from a        facility (petrochemical plant or utility power plant) is used to        regenerate the steam used for heating the sorbent structure. The        re-use of the CO₂ saturated steam eliminates the requirement to        treat large quantities of acidic water.

The technique referred to as “steam stripping with purge gas” works inthe following way:

-   -   a. Air is passed through the channels in the sorbent structure        and the CO₂ is removed from the air by the sorbent structure        until the sorbent structure reaches a specified saturation level        or the CO₂ level at the exit of the sorbent structure reaches a        specified value denoting that CO₂ breakthrough has started, or        for a specified time period determined by testing.    -   b. The sorbent structure is removed from the air stream and        isolated from the air flow and from air ingress and CO₂        migration to the outside air.    -   c. In order to remove oxygen from the channels in the sorbent        structure a purge of inert gas is passed through the sorbent        structure for a short time period.    -   d. Low pressure steam is passed through the channels in the        sorbent structure. The steam will initially condense and        transfer its latent heat of condensation to the sorbent        structure in the front part of the sorbent structure. The heat        of condensation raises the temperature of the sorbent structure        and provides energy to drive the CO₂ desorption process from the        sorbent structure. Eventually the front part of the sorbent        structure will reach saturation temperature and the liberated        CO₂ will be pushed out by the steam or extracted by a fan. This        process will move deeper into the sorbent structure from the        front part of the sorbent structure where the steam enters until        the CO₂ is liberated (note the fraction released will depend        upon the sorbent structure and temperature steam used). Only an        adequate amount of steam will be provided to achieve desorption        of the CO₂ from the sorbent structure so as to minimize the        steam used and minimize the amount of steam mixed in with the        liberated CO₂). As the condensate and then the steam pass        through the sorbent structure and heat the sorbent the CO₂ will        be liberated from the sorbent structure and be transferred into        the steam and condensate. The condensate will have a limited        ability to “hold” the CO₂ and once saturated the “sour” water        will not hold any more CO₂ and the CO₂ will remain in the vapor        phase as it is pushed out by the steam or extracted with a fan.        Once the steam has passed through the sorbent structure it has        to be condensed to liberate the CO₂. This is achieved in the        condenser which uses cooling water to remove the heat. The        collected stream will have some steam mixed in that will be        minimized to the extent possible, and that steam has to be        condensed to separate it from the CO₂. Alternatively the steam        could be condensed, using heat loss to the atmosphere, in an        uninsulated pipe or a finned pipe. This heat is a loss to the        system although an alternative would be to use the air exiting        the sorbent structure in the adsorption step (Step 1 above) to        condense the steam. This would raise the temperature of the air        at the exit of the sorbent structure and provide an additional        driving force to move the air through the sorbent structure and        reduce the energy requirements.    -   e. In order to cool the sorbent structure before it is replaced        in the air stream an inert gas is passed through the sorbent        structure until it is cooled to a specified temperature so that        damage to the sorbent structure will not occur when it is placed        back into the air stream.    -   f. Once the sorbent has had the CO₂ removed and the sorbent        structure cooled then the sorbent structure is raised up back        into the air stream. The air will continue to cool the sorbent        structure and remove any remaining moisture. The sorbent        structure will then remove the CO₂ until the specified        breakthrough occurs (see Step 1) and the sorbent structure is        then lowered into the regeneration position and the process        repeated.    -   g. The condensate from the desorption process (removing the CO₂        from the sorbent structure) contains CO₂ at saturation levels.        This condensate will be close to saturation temperature (as only        sufficient steam is added to the system to achieve CO₂ removal)        and is recycled to a boiler where low pressure steam from a        facility (petrochemical plant or utility power plant) is used to        regenerate the steam used for heating the sorbent structure. The        re-use of the CO₂ saturated steam eliminates the requirement to        treat large quantities of acidic water.

It should be noted that in each of the steam stripping techniquesdescribed above, there are two closed steam loops connected by a heatexchanger. One steam loop supplies the process heat and returns to theboiler hot condensate that results from heating the loop that does thesteam stripping. The other steam loop is the steam loop that does thesteam stripping and regeneration of the sorbent structure.

Steam stripping, as described above, would be performed in the foregoingmanner while the sorbent structure is disposed in the regeneration box1014 shown and described in connection with FIGS. 10 a, 10 b. Once thesorbent structure has had the CO₂ removed then the sorbent structure israised from the regeneration box 1014 back into the carbon dioxide ladenair stream, as also shown and described in connection with FIGS. 10 a,10 b. The carbon dioxide laden air stream will cool the sorbentstructure and remove any remaining moisture. The sorbent structure willthen remove the CO₂ until the specified breakthrough occurs and thesorbent structure is then lowered into the regeneration position inregeneration box 1014.

Sorbent Characteristics

In general, the sorbent that forms the sorbent structure ischaracterized by its ability to adsorb (bind CO₂) at low temperature andconcentration and regenerate at high temperature and high concentration(because CO₂ that is captured by the sorbent structure would have a highCO₂ concentration). Since the concentration of CO₂ in CO₂ laden air ison the order of 300 times smaller than the concentration of CO₂ in fluegases (a major contributor to the presence of CO₂ in the atmosphere),the CO₂ is captured from a stream of CO₂ laden air at ambienttemperature (e.g. about 20 degrees C. in many climates) and thetemperature of the steam used in the steam stripping process describedabove is at a temperature of about 100-120 degrees C., based on theLangmuir isotherm or Langmuir adsorption equation (which is known tothose in the art), the sorbent coverage of the sorbent structure shouldnot be too high at the lower temperature at which the CO₂ is captured,because that will increase the temperature required to remove the CO₂from the sorbent structure. Thus, while the sorbent material ispreferably an amine, the specific amine material or other suitablesorbent may vary for different climates to optimize the net CO₂ that iscollected during each cycle of capture and regeneration in which thesystem and process of the present invention will be used.

Co-Generation and Process Heat

As explained above, according to the present invention, process heat isused to provide the steam that is used in the “steam stripping” processand system described herein, to remove CO₂ from the sorbent structureand regenerate the sorbent structure. It is also preferred that theprocess heat is provided by a co-generation process and system, where aprimary process (e.g. a petrochemical plant, a utility facility, etc.)produces steam that is provided directly to the system of the presentinvention and used to remove the CO₂ from the sorbent structure andregenerate the sorbent structure.

Industrial plants such as power stations and petrochemical plantsgenerate large amounts of steam. The higher the pressure at which thesteam is generated the higher the thermal efficiency that can beachieved and the use of co-generation systems (where gas turbinesgenerate electricity and the hot gases from the turbine are used togenerate more steam) also improves the overall thermal efficiency of aCO₂ capture system and process, according to the principles of thepresent invention.

There are many different designs of steam systems within thepetrochemical industry due to the different mix of electric and turbinedrivers for pumps and compressors, the temperature required for columnreboilers and preheating duties, etc. These affect both the amount ofsteam generated and also the number of pressure levels at which thesteam is supplied to the process. Given these qualifications a “typical”petrochemical steam system design includes steam that is generated atvery high pressure (VHP) by the large boilers and co-generationfacilities. This VHP steam is passed to turbines which are used to drivemotors or compressors and result in exhaust steam at lower pressures.The next levels of steam are HP and MP which are provided from theextraction turbines or by direct let-down from the VHP steam main. Thefinal steam level is LP and is provided by the exit steam from theturbines and by direct let-down. Each steam level provides steam todifferent users and any excess steam is passed down to the next steamlevel. Thus the LP steam receives all the steam that cannot be usedusefully at the higher steam levels. It is important to recognize thatin a petrochemical facility the steam system must be flexible asdifferent sections of the process may be off-line or starting-up,shutting down or be at lower than design rates at different times. Thisis different from a utility power plant where the steam only has toprovide one function—generating electricity.

The value of steam depends upon the pressure level. The base cost of theVHP steam is fixed by the capital and operating costs of generation.However, as the steam is reduced in pressure by passing through theturbines energy is generated and this reduces the cost of the steam.

In the case of the proposed use of LP steam to release the CO₂ from thesorbent structure the following advantages appear to exist for a typicallarge petrochemical facility:

-   -   a. At a proposed steam level for the present invention (2-10        psig) the cost of the required steam will be very low for a        typical facility, although this will vary between facilities        depending upon the amount of LP that is available.    -   b. In comparison with a conventional amine system that requires        steam at approximately 60 psig the cost of steam at this level        will be significantly higher than for the 2-10 psig steam. In        addition it is much more likely that there will not be an        adequate supply of 60 psig available and that additional VHP        steam would have to be generated. This would raise the cost of        the 60 psig steam as it would either have to be charged at the        full cost of VHP steam or additional turbines would have to be        installed to recover power, but this would involve significant        capital costs.

In most power plants a steam supply is extracted from the low pressureturbine to heat the feed water to the system. This extraction steamwould be suitable for use in the proposed process to remove CO₂ from thesorbent structure as it is in co-generation of electricity andindustrial heat. In the cogeneration of electricity and CO₂ described inthis embodiment it is possible to use very low pressure (2 lb aboveatmosphere pressure and temperature around 105 C) and can return thecondensate to heat the boiler since the process heat being used is onlythe latent heat of the steam. While cogeneration of electricity andindustrial heat reduces the electricity produced it does raise theoverall thermal efficiency of using the heat generated to useful energyfrom 35-40% to 85-95%. It is thus favored when there are nearby uses forthe low temperature and pressure steam (usually 120 deg C., 2 lbs aboveatmosphere steam). In the cogeneration of electricity and CO₂ captureone can site the facility close enough to use the low temperature andpressure steam and by being able to use even lower pressure andtemperature steam and recirculating the hot condensate in the processheat steam loop back to heat the boiler minimize the impact onelectricity generation and thus the cost of the steam.

Sorbant Coated Pellet Structure and Concept of FIGS. 11 a, 11 b

FIGS. 11 a, and 11 b show 2 examples of another structure and techniquefor removing carbon dioxide from a flow of carbon dioxide laden air, andregenerate a sorbent used to absorb or bind to the carbon dioxide, inaccordance with the principles of the present invention.

In the structures and techniques of FIGS. 11 a and 11 b, particles,preferably of pellet size, flow by gravity into a pellet feedsource/storage bin 1100. The pellets are coated with the sorbent (e.g.an amine) that absorbs or binds carbon dioxide in a flow of carbondioxide laden air that flows through the pellets. The pellets can beselectively fed through a valve structure 1102 into an air contactingvessel 1104, and a flow of carbon dioxide laden air is directed throughthe vessel 1104, so that the sorbent absorbs or binds the carbon dioxideand removes the carbon dioxide from the air. A regeneration bin 1106 isprovided below the air contacting vessel 1104. The pellets can beselectively directed into the regeneration bin 1106, where process heatis directed at the pellets, to remove carbon dioxide from the sorbentand regenerate the sorbent. The pellets with the regenerated sorbent arethen directed to a vertical lifting structure 1108, where they areredirected to a location that enables them to flow into the feedsource/storage bin 1100 continue the carbon dioxide removal process. Thevertical lifting structure 1108 can comprise, e.g. an air blownstructure, an elevator, a screw conveyer, etc, that directs the pelletsback to the location that enables them to restart the carbon dioxideremoval process. The difference between the systems and techniques ofFIGS. 11 a and 11 b is that in the system and technique of FIG. 11 a,the carbon dioxide laden air flows downward through a mass of pelletscontained in the air contacting vessel 1104, whereas in the system andtechnique of FIG. 11 b, the carbon dioxide laden air flows horizontallythrough the pellets are then are flowing into the air contacting vessel1104.

The structure and techniques of FIGS. 11 a, 11 b are useful in removingcarbon dioxide from carbon dioxide laden air, and may also be useful inremoving carbon dioxide from flue gases that emanate from a source thatwould otherwise direct carbon dioxide into the atmosphere. Specifically,the structure and techniques of FIGS. 11 a and 11 b can be used toprovide sorbent coated pellets directly in the path of flue gases thatemanate from a source and would otherwise be directed into theatmosphere. The sorbent coated pellets can be used to remove carbondioxide from the flue gases, and the sorbent can then be treated withprocess heat, to remove the carbon dioxide from the pellets (so that itcan be drawn off and sequestered), and to regenerate the sorbent on thepellets (so that it can continued to be used to remove carbon dioxidefrom the flue gases).

It should also be noted that while the structures of FIGS. 11 a, 11 bare vertically oriented, it may be desirable that certain structures(e.g. the particle beds) be tilted (to facilitate water that condensesfrom steam during regeneration to drop to the bottom of the particle bedand not block the particle beds), or even oriented horizontally (also todeal with the condensed water issue).

Additional Comment Regarding Combining Air Stream with Flue Gas

The principles of the present invention can be applied in a new anduseful way to remove CO₂ from a combination of CO₂ laden air and fluegases (e.g. from a fossil fuel plant). A relatively large volume ratio(e.g. 98-99%) of CO₂ laden air is with a relatively small volume of fluegases (which contain a relatively high concentration of CO₂ that willultimately have to be removed from the CO₂ laden air) to produce a fluidstream in which the CO₂ in the flue gases adds sufficient CO₂ to the airto make the cost of removal of CO₂ more advantageous, and also providesbenefits in that the CO₂ laden air cools the flue gases. Application ofthe principles of the invention to produce such a fluid stream isbelieved to make the principles of the invention described aboveparticularly efficient. The CO₂ in the relatively large volume of CO₂laden air is still relatively low concentration, in accordance with abasic concept of applicants' paradigm, and the small volume amount offlue gases increase the concentration of CO₂ in the fluid stream, andmakes the applicant's process even more cost efficient in the manner inwhich it removes CO₂ from an ambient fluid stream. At the same time, theambient air cools the flue gases, in a manner that enables the processto function with an amine as the sorbent, which is believed to beefficient because the process can remove CO₂ from the sorbent, andregenerate at low temperature range, and the amine can be efficientlyregenerated.

In Summary

Accordingly, with the structure and technique of FIGS. 10 a-10 h, carbondioxide laden air is directed through the vertically oriented carbondioxide capture structure 1000 that has sorbent that absorbs or bindscarbon dioxide, to remove carbon dioxide from the air, the verticallyoriented carbon dioxide capture structure is lowered into a regenerationenclosure 1014, where process heat is directed at the carbon dioxidecapture structure, to separate carbon dioxide from the sorbent, andregenerate the sorbent, and the carbon dioxide capture structure 1000 isselectively raised out of the regeneration enclosure and to a positionthat is in the flow of carbon dioxide laden air, so that the regeneratedsorbent can continue to be used to absorb or bind carbon dioxide, toremove carbon dioxide from the flow of carbon dioxide laden air.Moreover, With the structure and technique of FIGS. 11 a, 11 b, a flowof sorbent carrying particles is selectively fed into a carbon dioxideremoval chamber 1104, a fluid is directed through particles in thecarbon dioxide removal chamber, so that carbon dioxide is absorbed orbound by the sorbent, to remove the carbon dioxide from the fluid, theparticles are directed to a carbon separation/regeneration chamber 1106,where process heat is used to separate carbon dioxide from the sorbent,and regenerate the sorbent carried by the particles, and the particleswith the regenerated sorbent are directed back to a particle feedsource, so that the particles with the regenerated sorbent can be reusedto absorb or bind carbon dioxide in the fluid.

Still further, the principles of the present invention can be providedin method of capturing CO₂, wherein a flow of CO₂ laden air is provided,a small amount (by volume) of flue gas is added to the flow of CO₂ ladenair, to produce a fluid flow in which the concentration of CO₂ issignificantly increased, in comparison to the CO₂ concentration in theflow of CO₂ laden air, and the fluid flow is passed through a sorbentstructure that binds CO₂ in the fluid flow.

Thus, the principles of the present invention are used to furtherdevelop the principles described in U.S. application Ser. No. 12/124,864(particularly the embodiment of FIG. 6 of that application), and todisclose further concepts for removing carbon dioxide from a fluid, inaccordance with the general principles of U.S. application Ser. No.12/124,864. With the foregoing disclosure in mind, it is believed thatvarious other ways of removing carbon dioxide from a fluid, inaccordance with the principles of this application, will become apparentto those in the art.

What is claimed is:
 1. A method of removing carbon dioxide from a carbondioxide-laden gas mixture of both predominantly ambient air and arelatively small amount (by volume) of effluent flue gas from a facilityoperating a primary process, comprising: directing a flow of carbondioxide-laden effluent flue gas from a facility operating a primaryprocess into contact with ambient air to form a carbon dioxide-laden gasmixture of predominantly ambient air, directing a flow of said carbondioxide-laden gas mixture of predominantly ambient air through amonolithic carbon dioxide capture structure disposed at a firstrelatively higher elevation that is supporting an amine sorbent capableof binding carbon dioxide to the sorbent, so as to remove carbon dioxidefrom the mixture, moving said monolithic carbon dioxide capturestructure from contact with said flow of carbon dioxide-laden gasmixture of predominantly ambient air into a regeneration enclosuredisposed at a second relatively lower elevation, regenerating thesorbent by causing saturated steam carrying process heat from saidprimary process at a temperature of not greater than about 120.degree.C. to come into contact with the carbon dioxide capture structure in theregeneration enclosure at said relatively lower elevation, therebycausing separation of carbon dioxide from the sorbent into theregeneration enclosure, withdrawing separated carbon dioxide from theregeneration enclosure, selectively moving the carbon dioxide capturestructure out of the regeneration enclosure from said second relativelylower elevation back to a position at said first relatively higherelevation disposed in the flow path of carbon dioxide-laden gas mixture,thereby permitting the regenerated sorbent to bind additional carbondioxide from the flow of said carbon dioxide-laden gas mixture,cyclically repeating said movements between said first and secondelevations of the monolithic carbon dioxide capture structure betweenthe regeneration enclosure and into contact with the carbondioxide-laden gas mixture of predominantly ambient air, and directingsaid withdrawn separated carbon dioxide to a storage structure, whereinsaid process heat from said primary process during said step ofregenerating the sorbent is provided by a co-generation process whereinprocess heat steam is directed at the carbon dioxide-capture structurein the regeneration enclosure.